Holderness coast

Holderness is the standard UK coastal case because the process is fast enough to see in a school lifetime. The cliffs are mostly glacial till — boulder clay dumped by ice, not lithified rock. Wave attack at the foot, sub-aerial weathering above, and a mass movement that is often a slump rather than a clean fall. Average erosion rates of one to two metres a year are widely cited from East Riding monitoring; locally the number is higher after a storm cluster.

The dominant wave approach is from the north-east. Swash runs up the beach at an angle; backwash returns down the steepest slope. Sediment therefore moves south in a longshore-drift conveyor. Spurn Head is the textbook spit at the southern end: a sand-and-shingle finger built where the coast turns into the Humber, with saltmarsh in the lee. It is not immortal. Storms breach it. The river and the sea then argue about where the mouth sits.

Mappleton’s rock groynes, placed in 1991, are a choice about whose beach is allowed to keep sand. Up-drift of a groyne, the beach widens. Down-drift, the supply is starved and erosion can accelerate. That is the classic ‘protection here, problem there’ sentence. Withernsea and Hornsea have sea walls and groynes of their own. Skipsea and the sites of lost villages such as Ravenser Odd sit on the other side of that bargain.

Constructive waves, with a strong swash, build a wider beach when the till supply and the drift allow it. Destructive waves, steeper, drag material back and attack the cliff. The Holderness fetch across the North Sea can throw destructive waves at a soft cliff for hours. Management options — do nothing, hold the line, managed realignment — are political, not just physical. The physics does not care about a caravan park. The budget does.

Compare a US barrier: the Outer Banks of North Carolina. There the sediment is sand in a barrier-island chain, not till in a cliff. Longshore drift still moves material alongshore. Storms still punch inlets. The landform is different; the budget idea is the same. Students who can say ‘supply, transport, deposition, interruption’ can move between Holderness and the Banks without learning a new subject.

Classroom move: run the coasts lab, turn on longshore particles, then freeze on the spit. Ask where a groyne would starve the spit. Then open this locator and point at Mappleton and Spurn. The 3D model is the process; this map is the place.